Field of the Invention
The present invention relates to a fuel cell formed by stacking an electrolyte electrode assembly and separators in a stacking direction. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes. Elastic seal members are formed integrally with the separators. A reactant gas flow field for supplying a reactant gas along an electrode surface is formed between the electrolyte electrode assembly and the separator. A reactant gas passage extends through the fuel cell in the stacking direction. The reactant gas passage is connected to the reactant gas flow field.
Description of the Related Art
For example, a solid polymer electrolyte fuel cell includes a unit cell which comprises a membrane electrode assembly (MEA) and a pair of separators sandwiching the membrane electrode assembly therebetween. The membrane electrode assembly includes an anode, a cathode, and an electrolyte membrane (electrolyte) interposed between the anode and the cathode. The electrolyte membrane is a polymer ion exchange membrane.
In use of the fuel cell of this type in a vehicle, normally, a predetermined number of (e.g., several tens to hundreds of) unit cells are stacked together to form a fuel cell stack, in order to generate a desired power generation output. In general, the fuel cell stack adopts so called internal manifold structure where reactant gas flow fields for allowing reactant gases to flow in the separators along electrode surfaces, and reactant gas passages communicating with the reactant gas flow fields and which extend through the unit cells in the stacking direction are provided.
In the fuel cell, as separators, carbon separators or metal separators are used. As the metal separator, a metal separator integral with a seal member, including a thin metal plate and an elastic seal member formed integrally with the thin metal plate is used.
In the metal separator of this type, in the case where a highly humid reactant gas, a coolant water, or the like flows continuously, water permeated into a rubber serving as a seal member may be retained between the seal member and the metal plate undesirably. As a result, blisters are formed between the seal member and the metal plate, the cross sectional area of the flow field is reduced, and the flow rate of the reactant gas or the coolant water is accordingly decreased.
In this regard, for example, a fuel cell separator disclosed in Japanese Laid-Open Patent Publication No. 2007-134204 is known. The fuel cell separator has a structure where a space facing a surface of an anode side metal separator is provided as a coolant passage, and an insulating film is formed on the surface through a primer layer. In this structure, coolant discharge grooves are formed to prevent formation of blisters due to condensation of coolant vaporized at the interface between a base material and the primer layer.
In the structure, the temperature of a portion of the anode side metal separator that partially contacts the primer layer is lowered. Even if the coolant component vaporized at the interface therebetween is condensed to liquid, since the condensed component is discharged to the outside through the coolant discharge grooves, formation of the blisters can be prevented.